Conventionally, a lighting device is known as this type of load control device. The lighting device comprises of a power inverter part to convert DC power AC power, discharging lamps driven by the power inverter part, a detection part to detect current value and voltage value of the discharge lamps, an A/D converter to convert analog current value and analog voltage value of discharge lamp into digital values respectively, an operation part to calculate a reference value standard value for control of the power inverter part according to a digital amount detected by A/D converter and a control part to control the inverter part based on the reference value (for example, refer to patent document 1: JP 1998-41079, pages 3 to 4, FIG. 1).